Alkyl nitroacetates are known compounds which are useful as intermediates to prepare various pharmaceutical and pesticidal products. Several methods are known to prepare alkyl nitroacetates, but none of them has proven commercially successful due to their high costs or potential health hazard.
U.S. Pat. No. 3,026,352 discloses the preparation of ethyl nitroacetate by self condensation of 2 mols of nitromethane in the presence of 4 mols of potassium hydroxide to form the dipotassium salt of nitroacetic acid followed by acidification and esterification.
Finkbeiner et al. have disclosed in J. Org. Chem., 28, 215-217 (1963) a process whereby nitromethane is treated with an excess of magnesium methyl carbonate to form the magnesium chelate of nitroacetic acid followed by esterification with a strong acid.
Kornblum et al. reported in J. Am. Chem. Soc., 77, 6654-5 (1955) that they prepared ethyl nitroacetate by reacting ethyl iodoacetate with silver nitrite.
Relatively high yields of the desired alkyl nitroacetate are prepared by these methods, but they are not suitable as a commercial route to formation of alkyl nitroacetate compounds due to the high cost of starting materials such as nitromethane, magnesium and silver.
Another route was disclosed by early researchers Bouveault and Wahl, Bull. Soc. Chim. France, 31, 847-54 (1904), whereby ethyl acetoacetate was reacted with absolute nitric acid in acetic anhydride at 30.degree.-35.degree. C., but low yields of ethyl nitroacetate were reported. This work was later confirmed by Arndt and Rose in J. Chem. Soc. 1935, 1-10. The major product produced using the conditions of Bouveault and Wahl was found to be diethyl2-oxofurazan dicarboxylate.
U.S. Pat. No. 3,761,510 discloses the preparation of alkyl nitroacetates by reaction of an acyl nitrate and an alkyl acetoacetate in the presence of an acid catalyst at low temperature to form an alkyl nitroacetoacetate intermediate. The alkyl nitroacetoacetate intermediate is cleaved with a nucleophile to form the corresponding alkyl nitroacetate. Although good yield of the alkyl nitroacetate was reported, this process is not a suitable commercial route since it presents a serious safety concern by requiring the preparation and isolation of the potentially explosive acetyl nitrate intermediate.